Sometimes, but I also look at the story and artwork as well. Seeing my favorite VA in the cast would either motivate me to check out an anime or be a bonus onto an anime that I was already looking forward to. Saying that, I also love to watch anime with new VA's just because you don't know their personalities and types of characters they voice yet, unlike veterans.

I personally like anything that has Tomokazu Sugita or Kana Hanazawa in the mix.

If I know a voice actor/actress is voicing on the anime, I will look into more information on said anime but I usually only do that with dubs [love Vic Mignogna.] But I will not chose a show just on the voice actors alone [I hated the dubbed version of Level E and it has one of my top fave voice actors in it, named above.] So it is one way to find anime to look into more.

I can't say I watch an anime because of the seiyuu, but if Hanazawa Kana is in it I consider it a big plus. I guess you could say I have a bit of a fanboy crush on her. I also like Sawashiro Miyuki's voice acting. There are several shows that have both of them, like Bakemonogatari/Nisemonogatari, Zetsuen no Tempest, Durarara!!, Black Rock Shooter, Deadman Wonderland, and Psycho-Pass. I think that's all of them. . .

With the exception of Deadman Wonderland, those were all great shows, so if I see that both of them are in a new anime I'll probably give it a chance even if the story synopsis doesn't pique my interest. Most of the time I don't check out those details ahead of time anyway though.

I can't imagine why you would watch a terrible show just because it had some voice actor you liked. and why do the weaboos insist on calling them "Seiyuus" while also speaking in English it just makes you sound like an ignorant Japanophile.